1. Technical Field
The present invention relates to photoresist polymers and photoresist compositions comprising the same. More specifically, it relates to compounds represented by Formula 1 described herein as photoresist monomers, photoresist polymers containing the same, and photoresist compositions that have excellent transmittance, etching resistance, thermal resistance, adhesive property, and low light absorbance at a wavelength of 13 nanomometers (nm) as well as 193 nm and 157 nm and high affinity to a developing solution, thereby improving line edge roughness (hereinafter, referred to as “LER”).
2. Description of the Related Art
In order to be used as photoresists for ArF and VUV (vacuum ultraviolet), photoresist polymers and photoresist compositions are required to have low light absorbance at wavelengths of 193 nm and 157 nm, excellent etching resistance and adhesive property on the substrate, and to be developed with 2.38 wt % and 2.6 wt % TMAH solution. Recently, much research has been focused to develop resins having high transparency at 248 nm and 193 nm wavelengths and etching resistance similar to novolac resin.
However, since the thickness of photoresist materials becomes thinner as circuits of semiconductor devices become more microfine, it is difficult to improve the LER of the patterns. Conventional photoresist materials have also strong light absorbance at a wavelength of 157 nm, thus they are improper for use at 157 nm wavelength.
The LER occurs more frequently in ArF photoresist patterns than in conventional KrF or I-line photoresist patterns. The conventional KrF or I-line photoresist materials include acidic alcohol groups while most ArF photoresist materials include no acidic alcohol group. As a result, since the ArF photoresist materials have low affinity to basic development solutions, the LER occurs more severely when using ArF photoresist materials.
In order to solve the above-described problems, polyethylene and polyacrylate resins comprising fluorine have been used. However, such polyethylene and polyacrylate resins comprising fluorine have low etching resistance and decreased adhesive properties to a silicon substrate.
Furthermore, the polyethylene and polyacrylate resins are not suitable to be used commercially because they are expensive and their mass-production is difficult. Moreover, the protecting group of the conventional photoresist polymer is destroyed in the baking process after exposure and generates gases when patterns are formed using chemically-amplified photoresists, resulting in the damage of the lens.
This phenomenon occurs inevitably when patterns are formed using chemically amplified photoresists, and decreased stability of the subsequent processes results in the reduction of the yield of the semiconductor devices.